Wheel Motor Device

ABSTRACT

A wheel motor device according to the present invention includes a hydraulic motor main body forming an HST in cooperation with the hydraulic pump main body, a motor shaft supporting the hydraulic motor main body in a relatively non-rotatable manner, a speed-reduction gear mechanism for reducing the speed of the rotational power output from the motor shaft, a first output member for outputting the rotational power whose speed has been reduced by the speed-reduction gear mechanism toward a corresponding first driving wheel, a casing accommodating the hydraulic motor main body and the speed-reduction gear mechanism, and a brake mechanism selectively and operatively applying a brake force to the first output member. The brake mechanism includes a brake shaft supported by the casing, a speed-increasing gear mechanism for increasing the speed of the rotational power output from the motor shaft and operatively transmitting the same to the brake shaft, and a brake unit for selectively and operatively applying the brake force to the brake shaft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wheel motor device which has ahydraulic motor main body forming an HST in cooperation with a hydraulicpump main body that is operatively driven by a drive source and which isplaced separately from the hydraulic pump main body such that it can bepositioned close to a corresponding driving wheel.

2. Related Art

There has been conventionally known a wheel motor device which has ahydraulic motor main body forming an HST in cooperation with a hydraulicpump main body that is operatively driven by a drive source and which isplaced separately from the hydraulic pump main body such that it can bepositioned close to a corresponding driving wheel (see, for example,Japanese Unexamined Patent Publication No. 2006-096112, JapaneseUnexamined Patent Publication No. 2005-195070, and Japanese UnexaminedPatent Publication No. 2005-028914, which are hereinafter referred to asprior document 1 to 3, respectively).

The wheel motor device can be preferably used in a working vehicle suchas a mid-mount mower tractor which is required to ensure a free spacebetween a pair of driving wheels usable as an installation space for arear discharge duct and the like.

More specifically, the wheel motor devices described in the priordocuments 1 to 3 include a speed-reduction gear mechanism for reducing aspeed of the rotational power output from the hydraulic motor main body,an output member for outputting the rotational power whose rotationalspeed has been reduced by the speed-reduction gear mechanism to thecorresponding driving wheel, and a brake mechanism capable ofoperatively and selectively applying a braking force to the outputmember, in addition to the hydraulic motor main body fluidly connectedto the hydraulic pump main body.

Since the conventional wheel motor devices include the speed-reductiongear mechanism, it is possible to employ a high-rotation/low-torque typehydraulic motor main body as the hydraulic motor main body. This canreduce the size of the hydraulic motor main body and also can reduce theleak of the hydraulic fluid from the hydraulic motor main body, therebyenhancing power transmission efficiency of the HST.

Meanwhile, it is desirable to reduce the size of the wheel motor deviceincluding the above-described components with respect to the directionof the rotational axis line of the corresponding driving wheel (namely,in the widthwise direction of the working vehicle).

Namely, by reducing the size of the wheel motor device in the directionof the rotational axis line, it is possible to ensure the free spacebetween the pair of driving wheels as much as possible.

Further, the wheel motor device is desired to reduce the size of thebrake mechanism as much as possible, while increasing the degree offreedom in designing the brake mechanism.

However, there exists no wheel motor device capable of attaining theabove-described two requirements at the same time.

Specifically, the wheel motor device described in the prior document 1includes a motor shaft positioned inwards in the vehicle widthwisedirection than the corresponding driving wheel with being parallel tothe rotational axis line of the corresponding driving wheel, a hydraulicmotor main body supported on the motor shaft in a relativelynon-rotatable manner, a speed-reduction gear mechanism operativelyconnected to an outer end portion of the motor shaft in thevehicle-widthwise direction (the end portion on as side close to thedriving wheel), an output member for outputting the rotational powerinputted from the speed-reduction gear mechanism to the driving wheel,and a brake mechanism positioned inwards in the vehicle-widthwisedirection than the hydraulic motor main body in such a way as toselectively apply a braking force to an inner end portion of the motorshaft in the vehicle-widthwise direction (the end portion on a side awayfrom the driving wheel).

Since the wheel motor device described in the prior document 1 isconfigured so that the brake mechanism applies the braking force to themotor shaft which is positioned on an upstream side in a powertransmission direction than the speed-reduction gear mechanism, it ispossible to achieve a reduction of the brake capacity required for thebrake mechanism, thereby reducing the size of the brake mechanism.

However, the brake mechanism is positioned inwards in thevehicle-widthwise direction than the hydraulic motor main body, therebyinducing the problem that the free space between the pair of drivingwheels is reduced due to the presence of the brake mechanism.

The wheel motor device described in the prior document 2 includes amotor shaft placed positioned inwards in the vehicle-widthwise directionthan the corresponding driving wheel with being parallel to therotational axis line of the corresponding driving wheel, a hydraulicmotor main body supported on the motor shaft in a relativelynon-rotatable manner, a speed-reduction gear mechanism operativelyconnected to an outer end of the motor shaft in the vehicle-widthwisedirection, an output member for outputting the rotational power inputtedfrom the speed-reduction gear mechanism to the driving wheel, and abrake mechanism inserted between the speed-reduction gear mechanism andthe outer end of the motor shaft in the vehicle-widthwise direction, inthe direction of the rotational axis line (in the vehicle-widthwisedirection) in such a way as to selectively and operatively apply abraking force to the output member.

Since the wheel motor device described in the prior document 2,similarly to the wheel motor device described in the prior document 1,is configured so that the brake mechanism applies the braking force tothe motor shaft which is positioned on an upstream side in a powertransmission direction than the speed-reduction gear mechanism, it ispossible to achieve a reduction of the brake mechanism in size.

However, the brake mechanism is positioned between the motor shaft andthe speed-reduction gear mechanism with respect to the vehicle-widthwisedirection, thereby inducing the problem that the free space between thepair of driving wheels is reduced due to the presence of the brakemechanism.

The wheel motor device described in the prior document 3 includes amotor shaft positioned inwards in the vehicle-widthwise direction thanthe corresponding driving wheel with being parallel to the rotationalaxis line of the corresponding driving wheel, a hydraulic motor mainbody supported on the motor shaft in a relatively non-rotatable manner,a speed-reduction gear mechanism operatively connected to an outer endof the motor shaft in the vehicle-widthwise direction, an output memberfor outputting the rotational power inputted from the speed-reductiongear mechanism to the driving wheel, and a brake mechanism configured soas to selectively apply a braking force to an intermediate shaft in thespeed-reduction gear mechanism.

More specifically, the speed-reduction gear mechanism includes theintermediate shaft which is placed at a position displaced from both themotor shaft and the output member with being parallel to both theshafts, a first speed-reduction gear train for performing primaryspeed-reduction between the motor shaft and the intermediate shaft, anda second speed-reduction gear train for performing secondaryspeed-reduction between the intermediate shaft and the output member.

Further, the brake mechanism is positioned so as to selectively andoperatively apply the braking force to the outer end portion of theintermediate shaft in the vehicle-widthwise direction (the end portionon a side away from the driving wheel).

Since the motor wheel device described in the prior document 3, thebrake mechanism is configured so as to apply the braking force to theintermediate shaft displaced from the motor shaft, it is possible toprevent the wheel motor device from being lengthened in thevehicle-widthwise direction (in the direction of the axis line of themotor shaft) due to the provision of the brake mechanism, therebypreventing the occurrence of the problem that the free space between thepair of driving wheels is reduced due to the presence of the brakemechanism.

However, in the wheel motor device described in the prior document 3,the position at which the brake mechanism is placed depends on theposition of the intermediate shaft in the speed-reduction gearmechanism, thereby degrading the degree of freedom in designing thebrake mechanism.

Further, in the prior document 3, the speed-reduction gear mechanismapplies the braking force to the intermediate shaft which is rotated ata rotational speed which has been reduced from the rotational speed ofthe motor shaft by the first speed-reduction gear train.

This structure induces the problem that the brake capacity of the brakemechanism cannot be sufficiently reduced.

SUMMARY OF THE INVENTION

The present invention is made in view of the above-describedconventional techniques, and it is an object to provide a wheel motordevice including a hydraulic motor main body, a motor shaft, aspeed-reduction gear mechanism, an output member and a brake mechanism,the wheel motor device capable of reducing the size of the brakemechanism as much as possible without degrading the degree of freedom indesigning the brake mechanism.

The present invention provides, in order to achieve the object, a wheelmotor device applied in a working vehicle including a driving powersource, a hydraulic pump main body operatively driven by the drivingsource and a pair of first and second driving wheels facing to eachother along a widthwise direction of the vehicle, the wheel motor deviceincluding a hydraulic motor main body that forms an HST in cooperationwith the hydraulic pump main body, a motor shaft that supports thehydraulic motor main body in a relatively non-rotatable manner, aspeed-reduction gear mechanism for reducing the speed of the rotationalpower output from the motor shaft, a first output member for outputtingthe rotational power whose speed has been reduced by the speed-reductiongear mechanism toward the corresponding first driving wheel, a casingthat accommodates the hydraulic motor main body and the speed-reductiongear mechanism, and a brake mechanism that selectively and operativelyapplies a brake force to the first output member, the wheel motor devicebeing characterized in that the brake mechanism includes a brake shaftsupported by the casing, a speed-increasing gear mechanism forincreasing the speed of the rotational power output from the motor shaftand operatively transmitting the same to the brake shaft, and a brakeunit for selectively and operatively applying the brake force to thebrake shaft.

Since the wheel motor device according to the present invention isconfigured so as to apply the brake force to the brake shaft having arotational power whose speed is increased by the speed-increasing gearmechanism with respect to the rotational power of the first outputmember, it is possible to reduce the size of the brake mechanism.

Furthermore, the wheel motor device makes it possible to freely positionthe brake shaft, independently of a power transmission path from themotor shaft to the first output member through the speed-reduction gearmechanism, thereby enhancing the degree of freedom in designing thebreak mechanism.

In one embodiment, the casing may include a motor case which supportsthe motor shaft at a position displaced from a rotational axis line ofthe first driving wheel in such a manner that the motor shaft issubstantially parallel to the rotational axis line of the first drivingwheel and is rotatable around its axis line and which accommodates thehydraulic motor main body supported by the motor shaft, and a gear caseconnected to a side of the motor case which is close to the firstdriving wheel, the gear case supporting the first output shaft so as tobe positioned coaxially with the rotational axis line of the firstdriving wheel in a state of being rotatable manner around its axis lineand accommodating the speed-reduction gear mechanism.

In the configuration, the brake shaft is supported in a rotatable manneraround its axis line by the gear case at a position displaced from thefirst driving wheel around the rotational axis line of the first drivingwheel, in such a manner that the brake shaft is substantially parallelto the rotational axis line of the first driving wheel and an endportion of the brake shaft on a side away from the first driving wheelis extended outward from the gear case.

The brake unit includes a brake disk supported by theoutwardly-extending end portion of the brake shaft in a relativelynon-rotatable manner, and is configured so as to selectively apply thebrake force to the brake disk on the basis of an operation from theoutside.

According to the one embodiment, it is possible to prevent the wheelmotor device from being enlarged with respect to a direction along therotational axis lines of the first and second driving wheels due to theprovision of the brake mechanism, thereby ensuring a free space betweenthe pair of first and second driving wheels as much as possible.

In the one embodiment, the gear case is preferably configured to becapable of supporting the brake shaft at plural positions around therotational axis line of the first output member.

According to the configuration, it is possible to enhance the degree offreedom in positioning the brake mechanism.

More preferably, the plural positions may include first and secondportions which are symmetrical to each other with an imaginary verticalplane as a reference, the imaginary vertical plane passing through therotation axis line of the first output member.

According to the configuration, it is possible to have the brake shaftin a first wheel motor device for driving the first driving wheel andthe brake shaft in a second wheel motor device for driving the seconddriving wheel positioned coaxially with each other while employing apair of wheel motor devices having the same configurations to each otheras the first and second wheel motor devices.

In the various configurations in the one embodiment, the brake unitpreferably includes a mounting stay detachably connected to the gearcase, a brake operation shaft supported in a rotatable manner around itsaxis line by the mounting stay in a state that its axis line extendssubstantially parallel to a disk surface of the brake disk and its firstend portion having a non-circular cross-sectional shape overlaps withthe brake disk as viewed along the rotational axis line of the brakedisk, and a push-side brake pad supported by the first end portion insuch a manner as to come close to or separate from the brake disk inaccordance with the rotation of the brake operation shaft about the axisline.

More preferably, the brake unit may further include a fixed-side brakepad detachably supported by the gear case in such a manner as to face tothe push-side brake pad across the brake disk.

In the above various configurations in the one embodiment, the wheelmotor device preferably further include a brake-shaft-side couplingsupported in a relatively non-rotatable manner by a portion of the brakeshaft which is away from the first driving wheel than the brake disk.The brake-shaft-side coupling has a concave/convex engagement portion atan end surface on a side opposite from the corresponding first drivingwheel, the concave/convex engagement portion being opened toward theother second driving wheel.

In the above various configurations, the wheel motor device may furtherinclude a second output member which is operatively connected trough thespeed-reduction gear mechanism to the motor shaft and which outputs adriving force toward the second driving wheel.

In one embodiment, the first and second output members may be positionedcoaxially with each other.

In the configuration, the wheel motor device may further include adifferential gear mechanism that includes a ring gear operativelyconnected to the motor shaft, first and second side bevel gearsrespectively supported on the first and second output members in arelatively non-rotatable manner, a pinion shaft rotating along with thering gear, and a bevel pinion supported on the pinion shaft in arelatively rotatable manner in a state of being engaged with the firstand second side bevel gears.

A driving-side gear with a small diameter provided on the motor shaft soas to engage with the ring gear forms the speed-reduction gear mechanismin cooperation with the ring gear, and a driven-side gear with a smalldiameter provided on the brake shaft so as to engage with the ring gearforms the speed-increasing gear mechanism in cooperation with the ringgear.

According to the configuration, it is possible to differentially drivethe first and second driving wheels only by providing the single wheelmotor device.

Preferably, the motor shaft is displaced from the rotational axis linein a state of being substantially parallel to the rotational axis line,and the first output member is disposed coaxially with the rotationalaxis line of the first driving wheel.

In the arrangement, the speed-reduction gear mechanism includes adriving-side gear with a small diameter which is provided on the motorshaft in a relatively non-rotatable manner, and an output gear with alarge diameter which is provided on the first output member in arelatively non-rotatable manner and which is engaged with thedriving-side gear, the output gear being embodied by an internal gear.The brake shaft is provided with a driven-side gear with a smalldiameter which is engaged with the output gear. The output gear and thedriven-side gear form the speed-increasing gear mechanism.

According to the configuration, it possible to have the positions of theaxis lines of the motor shaft and the brake shaft come close to theposition of the axis line of the first output member while sufficientlyensuring a speed reducing ratio of the speed-reduction gear mechanismand a speed increasing ratio of the speed-increasing gear mechanism,thereby realizing miniaturization of the wheel motor device in a radialdirection.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, and other objects, features and advantages of the presentinvention will become apparent from the detailed description thereof inconjunction with the accompanying drawings wherein.

FIG. 1 is a schematic side view of a working vehicle to which a wheelmotor device according to a first embodiment of the present invention isapplied.

FIG. 2 is a schematic rear view of the working vehicle shown in FIG. 1.

FIG. 3 is a hydraulic circuit diagram of the working vehicle shown inFIGS. 1 and 2.

FIG. 4 is a vertical cross-sectional view of the wheel motor deviceaccording to the first embodiment.

FIG. 5 is an end view of the wheel motor device taken along the line V-Vin FIG. 4.

FIG. 6 is a vertical cross-sectional front view of the wheel motordevice, showing a state in which pair of driving wheels of the workingvehicle are driven at a differential-lock state.

FIG. 7 is an end view of a wheel motor device according to a modifiedembodiment of the first embodiment.

FIG. 8 is a schematic side view of a working vehicle to which a wheelmotor device according to a second embodiment of the present inventionis applied.

FIG. 9 is a schematic rear view of the working vehicle shown in FIG. 8.

FIGS. 10 is a vertical cross-sectional front view of the wheel motordevice according to the second embodiment.

FIG. 11 is an end view of the wheel motor device taken along the lineXI-XI in FIG. 10.

FIG. 12 is a vertical cross-sectional front view a wheel motor deviceaccording to a modified embodiment of the present invention.

FIG. 13 is an exploded perspective view of the wheel motor device shownin FIG. 12.

FIG. 14 is a vertical cross-sectional view of a wheel motor deviceaccording to another modified embodiment of the present invention.

FIG. 15 is a vertical cross-sectional view of a wheel motor deviceaccording to still another modified embodiment of the present invention.

FIG. 16 is a vertical cross-sectional view of a wheel motor deviceaccording to a comparative example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

Hereinafter, a preferred embodiment of a wheel motor device according tothe present invention will be described, with reference to the attacheddrawings.

First, there will be described an embodiment of a working vehicle 1A towhich wheel motor devices 300A according to the present embodiment areapplied.

FIGS. 1 to 3 respectively illustrate a schematic side view, a schematicrear view and a hydraulic circuit diagram of the working vehicle 1A.

As illustrated in FIG. 1 and FIG. 2, the working vehicle 1A is formed tobe a mid-mount mower tractor having a mower device 60 at the center inthe lengthwise direction of the vehicle and also having a rear dischargeduct provided between a pair of driving wheels 50(1) and 50(2).

Specifically, the working vehicle 1A includes a vehicle frame 10 havinga pair of main frames 11 that extends along the vehicle-lengthwisedirection, a driver's seat 20 supported by the vehicle frame 10, adriving power source 30 supported by the vehicle frame 10, a pair ofnon-driving wheels 40 (front wheels in the present embodiment) and apair of driving wheels 50(1), 50(2) (rear wheels in the presentembodiment) respectively positioned on one side and the other side inthe vehicle-lengthwise direction, the mower device 60 positioned betweenthe non-driving wheels 40 and the driving wheels 50(1), 50(2) withrespect to the vehicle lengthwise direction, a discharge duct 70positioned between the pair of driving wheels 50(1), 50(2) in order toguide the grass cut by the working machine to the outsides (rearward inthe present embodiment), a hydraulic pump unit 100 including a hydraulicpump main body 110 operatively driven by the driving power source 30,the pair of wheel motor devices 300A(1), 300A(2) which are positionedaway from the hydraulic pump unit 100 so as to be close to thecorresponding driving wheels 50(1), 50(2) and which include hydraulicmotor main body 410 fluidly connected to the hydraulic pump main body110 through a pair of first and second hydraulic fluid lines 200(1),200(2) so as to form an HST in cooperation with the hydraulic pump mainbody 110.

Further, in the present embodiment, as illustrated in FIG. 3, thehydraulic motor main bodies 410 in the pair of wheel motor devices300A(1) and 300A(2) are fluidly connected in parallel to the hydraulicpump main body 110 in the hydraulic pump unit 100.

Namely, the hydraulic motor main bodies 410 in the pair of wheel motordevices 300A(1) and 300B(2) are differentially driven by the hydraulicpump main body 100 by means of hydraulic effect.

Accordingly, as illustrated in FIG. 1 and FIG. 3, in the presentembodiment, the non-driving wheels 40 are formed to be steering wheelssteered by a steering operation member 21, such as a steering wheel,which is provided at the front of the driver's sheet 20.

As illustrated in FIG. 1, the driving power source 30 is supported in avibration-preventing manner on the vehicle frame 10 throughvibration-preventing rubbers 39.

More specifically, the vehicle frame 10 has, in addition to the pair ofmain frames 11, a cross member 12 which couples the pair of main framesto each other, wherein the driving power source 30 is supported in avibration-preventing manner on the cross member 12 through thevibration-preventing rubbers 39.

In the present embodiment, the driving power source 30 is of a verticalcrank shaft type in which an output shaft 31 extends vertically. Thedriving power source 30 is supported on the upper surface of the crossmember 12 through the vibration-preventing rubbers 39 at a state where atip end portion of the output shaft 31 extends below the cross member 12through an opening formed at the cross member 12.

As illustrated in FIG. 1 and FIG. 3, the output shaft 31 is operativelyconnected to a pump shaft 120, which will be described later, in thehydraulic pump unit 100, through a traveling-system transmissionmechanism 80 such as a pulley-and-belt transmission mechanism, and,also, is operatively connected to an input shaft 61 of the mower device60 through a PTO-system transmission mechanism 85 such as apulley-and-belt transmission mechanism.

Further, as a matter of cause, it is also possible to employ, as thedriving power source 30, a driving power source of a horizontal crankshaft type, instead of the vertical crank shaft type.

As illustrated in FIG. 1 to FIG. 3, the hydraulic pump unit 100 includesthe pump shaft 120 which is operatively driven by the driving powersource 30, the hydraulic pump main body 110 supported by the pump shaft120 in a relatively non-rotatable manner, and a pump case 130 whichsupports the pump shaft 120 in a rotatable manner around the axis lineand also accommodates the hydraulic pump main body 110.

In the present embodiment, the hydraulic pump main body 110 is of anaxial piston type. Namely, the hydraulic pump main body 110 includes apump-side cylinder block (not illustrated) supported by the pump shaft120 in a relatively non-rotatable manner, and plural pump-side pistons(not illustrated) which are accommodated in the pump-side cylinder blockin a relatively non-rotatable manner around the axis line of the pumpshaft and in a reciprocating manner along the axis line.

As described above, the hydraulic pump main body 110 and the hydraulicmotor main bodies 410 form an HST.

Accordingly, at least one of the hydraulic pump main body 110 and thehydraulic motor main bodies 410 is formed to be of a variabledisplacement type in which its suction/discharge amount could bechanged.

As illustrated in FIG. 3, in the present embodiment, the hydraulic pumpmain body 110 is of a variable displacement type, while the hydraulicmotor main bodies 410 are of a fixed displacement type.

Accordingly, as illustrated in FIG. 3, the hydraulic pump unit 100 has adisplacement adjustment mechanism 140 for changing the suction/dischargeamount of the hydraulic pump main body 110, in addition to theabove-described components.

The displacement adjustment mechanism 140 may include a movable swashplate (not illustrated) which directly or indirectly engages with freeend portions of the pump-side pistons to define the range in which thepump-side pistons reciprocates, and a control shaft 141 (see FIG. 1)which can be operated from the outside to slant the movable swash plate.

The control shaft 141 is supported by the pump case 130 in a rotatablemanner around the axis line, and the movable swash plate is slanted inaccordance with the rotation of the control shaft 141 about the axisline.

Namely, the control shaft 141 is supported by the pump case 130 in arotatable manner around the axis line, in a state where its inner endportion is operatively connected to the movable swash plate and itsouter end portion can be operated from the outside.

Further, the outer end portion of the control shaft 141 is operativelyconnected to a speed-changing operation member 22 (see FIG. 3) such as aspeed-changing pedal positioned in a vicinity of the driver's sheet 20,so that the control shaft 141 is rotated about the axis line inaccordance with a manual operation on the speed-changing operationmember 22.

In the present embodiment, the movable swash plate is configured so thatit can be slanted in both a forward direction and a rearward directionacross a neutral position.

Namely, when the speed-changing operation member 22 is operated in aforward side and a rearward side, the control shaft 141 is rotated inone direction and the other direction about the axis line, therebycausing the movable swash plate to be slanted in the forward andrearward directions.

Further, in the present embodiment, the speed-changing operation member22 is structured to be of a seesaw-pedal type, but it can be of atwo-pedal type including a dedicated forward pedal and a dedicatedrearward pedal.

As illustrated in FIG. 3, the pump case 130 is formed with various fluidchannels including a pair of pump-side hydraulic fluid channels 211which form portions of the pair of first and second hydraulic fluidlines 200(1) and 200(2).

More specifically, as illustrated in FIG. 1, the pump case 130 includesa hollow-shaped pump-side case main body 131 with an opening having asize that allows the hydraulic pump main body 110 to pass therethrough,and a pump-side port block 132 detachably coupled to the pump case mainbody 131 in such a way as to close the opening in a liquid-tight manner,wherein the fluid channels are formed in the pump-side port block 132.

As illustrated in FIG. 3, the pair of pump-side hydraulic fluid channels211 include a first pump-side hydraulic fluid channel 211(1) whichexperiences a higher pressure at a time of a forward movement of thevehicle and a second pump-side hydraulic fluid channel 211(2) whichexperiences a higher pressure at a time of a rearward movement of thevehicle.

The first pump-side hydraulic fluid channel 211(1) has a first endfluidly connected to the hydraulic pump main body 110 through a firstkidney port opened to a contacting surface of the pump-side port block132 to which the hydraulic pump main body 110 contacts in a rotatablemanner, and a second end opened to an outer surface of the pump-sideport block 132 to form a first pump-side hydraulic fluid port 212(1).

Similarly, the second pump-side hydraulic fluid channel 211(2) has afirst end fluidly connected to the hydraulic pump main body 110 througha second kidney port opened to the contacting surface of the pump-sideport block 132 to which the hydraulic pump main body 110 contacts in arotatable manner and a second end opened to the outer surface of thepump-side port block 132 to form a second pump-side hydraulic fluid port212(2).

A pair of first and second pump-side hydraulic fluid conduits 213(1),213(2) which form portions of the pair of first and second hydraulicfluid lines 200(1) and 200(2) are fluidly connected to the first andsecond pump-side hydraulic fluid ports 212(1) and 212(2), respectively.

Further, in the present embodiment, the working vehicle 1A includes thepair of wheel motor devices 300A(1), 300A(2) for driving the pair ofdriving wheels 50(1), 50(2), respectively, as described above, and thehydraulic motor main bodies 410 in the pair of wheel motor devices300A(1) and 300A(2) are fluidly connected in parallel to the singlehydraulic pump main body 110.

More specifically, the hydraulic motor main bodies 410 in the pair ofwheel motor devices 300A(1) and 300A(2) are fluidly connected to eachother through a first motor-side hydraulic fluid conduit 214(1) whichexperiences a higher pressure at a time of the forward movement of thevehicle and a second motor-side hydraulic fluid conduit 214(2) whichexperiences a higher pressure at a time of the rearward movement of thevehicle, as illustrated in FIG. 3.

The first and second pump-side hydraulic fluid conduits 213(1), 213(2)are fluidly connected to the first and second motor-side hydraulic fluidconduits 214(1), 214(2), respectively.

Further, as illustrated in FIG. 3, the pump-side port block 132 isformed with a charge fluid channel 220 for replenishing the pair offirst and second hydraulic fluid lines 200(1), 200(2) with a hydraulicfluid.

The charge fluid channel 220 has a first end fluidly connected to ahydraulic pressure source and second ends fluidly connected to the pairof first and second pump-side hydraulic fluid channels 211(1), 211(2)through first and second check valves 229(1), 229(2), respectively.

In the present embodiment, as illustrated in FIG. 3, the hydraulic pumpunit 100 further includes an auxiliary pump main body 150 whichfunctions as the hydraulic pressure source.

The auxiliary pump main body 150 is driven directly or indirectly by thepump shaft 120.

The auxiliary pump main body 150 has a suction side fluidly connected toa fluid source such as a fluid tank 90 and a discharge side fluidlyconnected to the charge fluid channel 220.

More specifically, as illustrated in FIG. 3, the pump-side port block132 is formed with a suction fluid channel 230 having a first end openedto the outer surface of the pump-side port block 132 to form a suctionport 231 and a second end fluidly connected to the suction side of theauxiliary pump main body 150, and a discharge fluid channel 240 having afirst end fluidly connected to the discharge side of the auxiliary pumpmain body 150 and a second end fluidly connected to the charge fluidchannel 220.

The suction fluid channel 230 is fluidly connected to the fluid sourcethrough a suction conduit 232 connected to the suction port 231. In FIG.3, there are shown a filter 235 inserted in the suction conduit, and adrain conduit 239 for returning the fluid stored in the pump case 130 tothe fluid source.

Further, as illustrated in FIG. 3, the pump case 130 is formed with acharge-pressure setting fluid channel 250 in which a relief valve 255for setting the hydraulic pressure in the charge fluid channel 220 isinserted.

The charge-pressure setting fluid channel 250 has a first end fluidlyconnected to the suction fluid channel 240 or the charge fluid channel220 and a second end fluidly connected to the suction fluid channel 230.

Further, the relief valve 255 is inserted in the charge-pressure settingfluid channel 250, in such a manner that its primary side is oriented tothe suction fluid channel 240 or the charge fluid channel 220 and therelieved fluid from the relief valve 255 is returned to the suctionfluid channel 230.

Further, as illustrated in FIG. 3, the pump-side port block 132 isformed with a bypass fluid channel 260 for communicating the first andsecond pump-side hydraulic fluid channels 211(1) and 211(2) to eachother, and a bypass valve 265 for selectively switching between thecommunication state and the shutoff state of the bypass fluid channel260.

By providing the bypass fluid channel 260 and the bypass valve 265, itis possible to effectively prevent the occurrence of a pressuredifference between the pair of first and second hydraulic fluid lines200(1), 200(2) at a time when the working vehicle 1A is forcibly towedin the event of failures of the driving power source 30, the HST or thelike, thereby allowing the left and right hydraulic motor main bodies410 for driving the first and second driving wheels 50(1), 50(2),respectively, to run at idle when forcibly towing.

Hereinafter, the wheel motor devices 300A will be described.

FIG. 4 illustrates a vertical cross-sectional view of the wheel motordevice 300A(1) (hereinafter, referred to as a first wheel motor device)for driving one of the pair of driving wheels 50(1) and 50(2)(hereinafter, referred to as a first driving wheel (50(1)).

Further, FIG. 5 illustrates an end view of the first wheel motor device300A(1) taken along the line V-V in FIG. 4.

Further, the wheel motor device 300A(2) (hereinafter, referred to as asecond wheel motor device) for driving the other one of the pair ofdriving wheels 50(1) and 50(2) (hereinafter, referred to as a seconddriving wheel 50(2)) has the same structure as that of the first wheelmotor device 300A(1), and the respective wheel motor devices aresymmetrically mounted with respect to the pair of main frames 11.

As illustrated in FIG. 4, the first wheel motor device 300A(1) includesa hydraulic motor unit 400 including the hydraulic motor main body 410which forms the HST in cooperation with the hydraulic pump main body110, a speed-reduction gear unit 500 including a speed-reduction gearmechanism 510 for reducing the speed of the rotational power output fromthe hydraulic motor main body 410, and a first output member 350(1) foroutputting, to the first driving wheel 50(1), the rotational power whosespeed has been reduced by the speed-reduction gear mechanism 510.

As illustrated in FIG. 4, the hydraulic motor unit 400 includes a motorshaft 420 which supports the hydraulic motor main body 410 in arelatively non-rotatable manner, and a motor case 430 which supports themotor shaft 420 in a rotatable manner about the axis line and alsoaccommodates the hydraulic motor main body 410, in addition to thehydraulic motor main body 410.

The hydraulic motor main body 410 includes a motor-side cylinder block411 supported by the motor shaft 420 in a relatively non-rotatablemanner, and plural motor-side pistons 412 accommodated in the motor-sidecylinder block 411 in a relatively non-rotatable manner around the axisline of the motor shaft and in a reciprocating manner along the axisline.

As described above, in the present embodiment, the hydraulic motor mainbodies 410 are of a fixed displacement type.

Accordingly, the hydraulic motor unit 400 includes a fixed swash plate440, in addition to the components.

The motor case 430 is coupled directly or indirectly to one of the pairof main frames 11.

In the present embodiment, as illustrated in FIG. 1 and FIG. 2, thevehicle frame 10 has a pair of mounting frames 15 extending downwardsfrom the pair of main frames 11 such that their plate surfaces are facedto the pair of driving wheels 50(1), 50(2), and the motor case 430 iscoupled to the corresponding one of the mounting frames 15.

Preferably, the pair of mounting frames 15 are coupled to each other attheir lower end portions through a reinforcing frame 16, as illustratedin FIGS. 1 and 2. This structure can increase the rigidity of thevehicle frame 10.

Further, in the structure where the pair of mounting frames 15 arecoupled to each other at their lower end portions through thereinforcing frame 16, the discharge duct 70 is passed through the spacedefined by the cross member 12, the pair of main frames 11, the pair ofmounting frames 15 and the reinforcing frame 16, as illustrated in FIG.2.

As illustrated in FIG. 3, the motor case 430 is formed with a pair ofmotor-side hydraulic fluid channels 215 which form portions of the pairof first and second hydraulic fluid lines 200(1) and 200(2).

More specifically, as illustrated in FIG. 4 and FIG. 5, the motor case430 has a hollow-shaped motor case main body 431 with an opening havinga size that allows the hydraulic motor main body 410 to passtherethrough, and a motor-side port block 432 detachably coupled to themotor case main body 431 in such a way as to close the opening in aliquid-tight manner, wherein the pair of motor-side hydraulic fluidchannels 215 are formed in the motor-side port block 432.

In FIG. 5, there are shown mounting holes 435 for coupling the motorcase 430 to the mounting frame 15, and coupling holes 436 for couplingthe motor case main body 431 and the motor-side port block 432 to eachother.

The pair of motor-side hydraulic fluid channels 215 include a firstmotor-side hydraulic fluid channel 215(1) which experiences a higherpressure at a time of the forward movement of the vehicle and a secondmotor-side hydraulic fluid channel 215(2) which experiences a higherpressure at a time of the rearward movement of the vehicle.

The first motor-side hydraulic fluid channel 215(1) has a first endopened to the outer surface of the motor-side port block to form a firstmotor-side hydraulic fluid port 216(1) and a second end fluidlyconnected to the hydraulic motor main body 410 through a first kidneyport opened to a contacting surface of the motor-side port block 432 towhich the hydraulic motor main body 410 contacts in a rotatable manner.

Similarly, the second motor-side hydraulic fluid channel 215(2) has afirst end opened to the outer surface of the motor-side port block 432to form a second motor-side hydraulic fluid port 216(2) and a second endfluidly connected to the hydraulic motor main body 410 through a secondkidney port opened to the contacting surface of the motor-side portblock 432 to which the hydraulic motor main body 410 contacts in arotatable manner.

As described above, in the present embodiment, the hydraulic motor mainbody 410 in the first motor device 300A(1) and the hydraulic motor mainbody 410 in the second motor device 300A(2) are fluidly connected to thesingle hydraulic pump main body 110 in such a manner that they areparallel with respect to the hydraulic pump main body 110.

Namely, as illustrated in FIG. 3, the first motor-side hydraulic fluidports 216(1) in the first and second wheel motor devices 300(1), 300A(2)are fluidly connected to each other through the first motor-sidehydraulic fluid conduit 214(1) and, also, the second motor-sidehydraulic fluid ports 216(2) in the first and second wheel motor devices300(1), 300A(2) are fluidly connected to each other through the secondmotor-side hydraulic fluid conduit 214(2).

Further, the first and second motor-side conduits 214(1), 214(2) arefluidly connected to the first and second pump-side hydraulic fluidconduits 213(1), 213(2), respectively.

As illustrated in FIG. 4, the motor case main body 431 is placed suchthat the opening is orientated inwards in the vehicle-widthwisedirection.

More specifically, the motor case main body 431 includes a hollowperipheral wall 431 a extending in the direction of the rotational axisof the hydraulic motor main body 410 in such a way as to surround thehydraulic motor main body 410, and an end wall 431 b which closes theend portion of the peripheral wall 431 a on a side closer to thecorresponding first driving wheel 50(1), wherein the end portion of theperipheral wall 431 a on a side away from the first driving wheel 50(1)forms the opening.

Further, the motor-side port block 432 is detachably coupled to the endportion of the motor case main body 431 on a side away from the firstdriving wheel 50(1) in such a way as to close the opening.

By making an arrangement that the motor-side port block 432, to whichthe first and second motor-side hydraulic fluid conduits 214(1), 214(2)are connected, is positioned on a side away from the first driving wheel50(1) with the motor case main body 431 as a reference, as describedabove, it is possible to insert the motor case main body 431 and/or agear case 530 coupled to the motor case main body 431, which will bedescribed later, into the wheel 55 of the corresponding first drivingwheel 50(1), as much as possible (see FIG. 4).

Accordingly, it is possible to expand the free space between the firstwheel motor device 300A(1) for driving the first driving wheel 50(1) andthe second wheel motor device 300A(2) for driving the second drivingwheel 50(2), as much as possible.

Preferably, as illustrated in FIG. 4, the motor-side port block 432 maybe formed with a cylindrical protrusion 432 a at the surface on a sideopposite from the side to which the motor case main body 431 is mounted,and the protrusion 432 a can be inserted into a circular hole 15 aformed in the mounting frame 15 to perform positioning the motor case430.

The motor shaft 420 is supported in a rotatable manner around the axisline by the motor-side port block 432, the end wall 431 b of the motorcase main body 431 and a gear case 530 which will be described later, ina state of being substantially parallel to the rotational axis line R ofthe corresponding first driving wheel 50(1), as illustrated in FIG. 4.

More specifically, as illustrated in FIG. 4, an end portion of the motorshaft 420 which is closer to the corresponding first driving wheel 50(1)is penetrated through the end wall 431 b and is extended into a gearspace 530S which will be described later, thereby forming an output endportion for outputting rotational power to the speed-reduction gearmechanism 510.

The speed-reduction gear unit 500 includes the gear case 530 whichaccommodates the speed-reduction gear mechanism 510 and which supportsthe first output member 350 in a rotatable manner around the axis line,in addition to the speed-reduction gear mechanism 510.

The gear case 530 is coupled to the motor case 430 in such a way as toform a casing of the wheel motor device 300A(1) in cooperation with themotor case 430.

In the present embodiment, the gear case 530 includes an inner-side casebody 531 formed integrally with the motor case 430, and an outer-sidecase body 532 detachably coupled to the inner-side case body 531.

More specifically, as illustrated in FIG. 4, the end wall 431 b of themotor case main body 431 has an extended wall 431 c extending in thedirection orthogonal to the motor shaft 420, and the extended wall 431 cforms the inner-side case body 531.

As a matter of cause, the inner-side case body 531 can be formedseparately from the motor case main body 431 and can be coupled to themotor case main body 431.

As illustrated in FIG. 4, the outer-side case body 532 is detachablycoupled to the side of the inner-side case body 531 which is closer tothe first driving wheel, in such a way as to define the gear space 530Sfor accommodating the speed-reduction gear mechanism 510 between theouter-side case body 532 and the inner-side case body 531.

The speed-reduction gear mechanism 510 is configured so as to reduce thespeed of the rotational power from the motor shaft 420 and transmit itto the first output portion 350(1).

In the present embodiment, as illustrated in FIG. 4, the speed-reductiongear mechanism 510 includes a driving-side gear 511 with a smallerdiameter which is provided on the output end portion of the motor shaft420, and an output gear 512 with a larger diameter which is provided onthe first output member 350(1) in a state of being engaged with thedriving-side gear 511.

In the present embodiment, as illustrated in FIG. 4, the first outputmember 350(1) is formed to be an output shaft.

More specifically, the first output member 350(1) is supported by thegear case 530 in a rotatable manner around the axis line in a state ofbeing positioned coaxially with the rotational axis line R of thecorresponding first driving wheel 50(1), and the end portion of thefirst output member 350(1) on a side closer to the first driving wheel50(1) is extended outwards and is coupled to the wheel 55 of the firstdriving wheel 50(1).

Further, in the present embodiment, the first and second wheel motordevices 300A(1), 300A(2) are mounted to the working vehicle in such amanner that they drive the non-steering wheels (the rear wheels in theillustrated embodiment), but the present invention is not limited tothis embodiment, as a matter of cause.

For example, there may be provided steering frames (not illustrated)which are respectively coupled to the left and right sides of thevehicle frame 10 through kingpins such that they can be steered and,also, the first and second wheel motor devices 300A(1), 300A(2) may bemounted to the left and right steering frames for driving the steeringwheels. With this structure, the first and second wheel motor devices300A(1), 300A(2) at the left and right sides are steered insynchronization with each other through a tie rod mounted to the gearcases 530 or the steering frames in the wheel motor devices 300A(1),300A(2).

Further, while, in the present embodiment, the hydraulic motor mainbodes 410 in the first and second wheel motor devices 300A(1), 300A(2)are fluidly connected in parallel with respect to the single hydraulicpump main body 10 as described above, instead of this structure, theworking vehicle may be provided with a pair of hydraulic pump mainbodies 110 and, also, the hydraulic motor main bodies 410 in the firstand second wheel motor devices 300A(1) and 300A(2) may be individuallyand fluidly connected to the pair of hydraulic pump main bodies 110.

As illustrated in FIG. 3 to FIG. 5, the wheel motor device 300A(1)includes a brake mechanism 600 for operatively and selectively applyinga braking force to the first output member 350(1), in addition to thecomponents.

As illustrated in FIG. 4 and the like, the brake mechanism 600 includesa brake shaft 610 supported by the casing, a speed-increasing gearmechanism 620 for increasing the rotational power from the first outputmember 350(1) and operatively transmitting it to the brake shaft 600,and a brake unit 630 for selectively applying a braking force to thebrake shaft 610.

The wheel motor device 300A(1) with the braking mechanism 600 can offerthe following effects.

Namely, the brake mechanism 600 is configured so as to apply the brakingforce to the brake shaft 610 which has a rotational speed increased bythe speed-increasing gear mechanism 620 so as to be higher than that ofthe first output member 350(1).

Accordingly, it is possible to reduce the brake capacity required forthe brake mechanism 600, thereby enabling reduction of the size of thebrake mechanism 600.

Further, the brake shaft 610 to which the braking force is operativelyapplied is independent of the transmission path for transmitting therotational power from the motor shaft 420 to the first output member350(1) through the speed-reduction gear mechanism 510. The configurationallows the brake shaft 610 to be placed at an arbitrary position,independently of the positions at which the motor shaft 420, thespeed-reduction gear mechanism 510 and the first output member 350(1)are installed, thereby increasing the degree of freedom in designing thebrake mechanism 60.

As illustrated in FIG. 4, the brake shaft 610 is provided with adriven-side gear 621 with a smaller diameter which engages with theoutput gear 512.

In this structure, the output gear 512 and the driven-side gear 621 formthe speed-increasing gear mechanism 620.

In the present embodiment, as illustrated in FIG. 4 and FIG. 5, thebrake shaft 610 is supported by the gear case 530 in a rotatable manneraround the axis line, in a state where its end portion on a side awayfrom the first driving wheel 50(1) is extended outwards and where it issubstantially parallel to the rotational axis line R of the firstdriving wheel 50(1), at a position displaced from the motor shaft 420about the rotational axis line R of the first driving wheel 50(1).

Further, the brake unit 630 has a brake disk 631 supported by theoutwardly-extending end portion of the brake shaft 610 in a relativelynon-rotatable manner, and is configured so as to selectively apply thebraking force to the brake disk 631 on the basis of an operation fromthe outside.

With this structure, it is possible to effectively prevent the freespace between the pair of driving wheels 50(1), 50(2) from being reduceddue to the provision of the brake mechanism 600.

Namely, as illustrated in FIG. 4, with the above-described structure, itis possible to position the brake unit 630 at the same position as thehydraulic motor main body 410 with respect to the rotational axis line Rof the first driving wheel 50(1) (in the vehicle-widthwise direction).

Accordingly, it is possible to prevent the wheel motor device 300A(1)from being expanded in the direction of the rotational axis line R ofthe first driving wheel 50(1) due to the provision of the brakemechanism 600, thereby ensuring the free space between the pair ofdriving wheels 50(1), 50(2) as much as possible.

As illustrated in FIGS. 4 and 5, the brake unit 630 includes a mountingstay 632 detachably supported on the end surface of the gear case 530 ona side opposite from the first driving wheel 50(1) (the outer surface ofthe inner-side case body 531, in the present embodiment), a brakeoperation shaft 633 supported by the mounting stay 632 in a rotatablemanner around the axis line in a state of being substantially parallelto the disk surface of the brake disk 631, and a push-side brake pad 634supported by the brake operation shaft 633 in such a way as to contactwith or separate from the brake disk 631 in accordance with the rotationof the brake operation shaft 633 about the axis line, in addition to thebrake disk 631.

More specifically, as illustrated in FIG. 4, the brake operation shaft633 has a first end portion 633 a having a non-circular cross-sectionalshape, wherein the push-side brake pad 634 is supported by the first endportion 633 a.

As illustrated in FIGS. 4 and 5, the brake operation shaft 633 issupported by the mounting stay 632 such that the first end portion 633 aoverlaps with the brake disk 631 as viewed along the rotational axisline of the brake disk 631.

The brake operation shaft 633 is operatively connected to a brakeoperation member (not illustrated) provided near the driving seat 20,through, for example, a link mechanism including a connecting arm 636coupled to the brake operation shaft 633 in a relatively non-rotatablemanner around the axis line of the brake operation shaft 633 (see FIGS.4 and 5).

In the present embodiment, the first end portion 633 a of the brakeoperation shaft 633 is formed with a concave portion at the outersurface which is faced to the brake disk 631, and the push-side brakepad 634 is placed within the concave portion.

In the present embodiment, the brake disk 631 is supported by the brakeshaft 610 in a movable manner along the axis line, in a state of beingrotated along with the brake shaft 610 around the axis line.

In order to effectively making it possible to apply a braking force tothe brake disk 631 having the above-described structure, the brake unit600 includes a fixed-side brake pad 635 detachably supported by the gearcase 530, such that the fixed-side brake pad 635 is faced to thepush-side brake pad 634 across the brake disk 631, as illustrated inFIG. 4.

While, in the present embodiment, the disk-brake type mechanism havingthe above-described structure is employed as the brake mechanism 60,instead of this mechanism, it is also possible to employ aninternal-expanding drum brake type mechanism or a band-brake typemechanism.

Preferably, as illustrated in FIG. 6, the brake shaft 610 whichconstantly rotates in synchronization with the motor shaft 420 can havesplines 611 at a portion away from the corresponding first driving wheel50(1) than the brake disk 631.

With this structure, it is possible to easily connect the brake shaft610 in the first wheel motor device 300A(1) for driving the firstdriving wheel 50(1) and the brake shaft 610 in the second wheel motordevice 300A(2) for driving the second driving wheel 50(2) to each otherin a relatively non-rotatable manner around their axis lines, therebymaking it possible to drive the first and second driving wheels 50(1),50(2) in a differential-lock state.

Namely, as described above, in the present embodiment, the hydraulicmotor main bodies 410 in the first and second wheel motor devices300A(1) and 300A(2) are fluidly connected in parallel with respect tothe hydraulic pump main body 110, and the first and second drivingwheels 50(1), 50(2) are therefore differentially driven by usinghydraulic effect.

With this structure, in the event that one of the first and seconddriving wheels 50(1) and 50(2) falls in a concave portion, a mud areaand the like so that the rotational load on this driving wheel isextremely reduced, the hydraulic fluid from the hydraulic pump main body110 is intensively flowed into the hydraulic motor main body 410 in thewheel motor device 300A(1) or 300A(2) for operatively driving thisdriving wheel. As a result, the hydraulic fluid is not supplied to thehydraulic motor main body 410 in the wheel motor device 300A(1) or300A(2) for operatively driving the other one of the driving wheels50(1) and 50(2), which may make it impossible to move the workingvehicle.

In order to avoid the occurrence of the such a state, in the presentembodiment, the brake shaft 610 in the first wheel motor device 300A(1)and the brake shaft 610 in the second wheel motor device 300A(2) couldbe coupled to each other using the splines 611 such that they arerelatively non-rotatable to each other about their axis lines.

More specifically, as illustrated in FIG. 6, the brake shaft 610 isprovided with a brake-shaft-side coupling 650 which is relativelynon-rotatable about the axis line with respect to the brake shaft 610through the splines 611. The brake-shaft-side coupling 650 has aconcave/convex engagement portion at an end surface on a side oppositefrom the corresponding first driving wheel 50(1), the concave/convexportion being opened toward the other driving wheel or the seconddriving wheel 50(2).

Meanwhile, the working vehicle 1A to which the wheel motor devices300A(1), 300A(2) are applied is provided with a differential-lockconnecting shaft 660.

The differential-lock connecting shaft 660 is provided in the workingvehicle 1A, such that it can be selectively positioned at adifferential-lock position that is coaxial with the brake shaft 610 (seeFIG. 6) and at a differential position that is displaced from the brakeshaft 610 (not illustrated).

The differential-lock connecting shaft 660 is formed with splines 661 atthe opposite ends and is provided with first and secondcoupling-shaft-side couplings 670 at one end and the other end in arelatively non-rotatable manner about the axis line through the splines661.

Each of the first and second coupling-shaft-side couplings 670 has aconcave/convex engagement portion opened toward the correspondingdriving wheel.

The switching between the differential state and the differential-lockstate is performed as follows.

The differential-lock connecting shaft 660 is positioned at thedifferential position, at an initial state.

At this state, there is realized a differential state where the firstand second driving wheels 50(1), 50(2) are differentially driven usinghydraulic effect.

On the other hand, in a case where it is necessary to perform thetransition from the differential state to the differential-lock state,an operator moves the differential-lock connecting shaft 660 from thedifferential position to the differential-lock position illustrated inFIG. 6 and, at this state, the first and second coupling-shaft-sidecouplings 670 are engaged with the brake-shaft-side couplings 650 in thefirst and second wheel motor devices 300A(1), 300A(2) in aconcave-to-convex manner.

Accordingly, the first output members 350(1) in the first and secondwheel motor devices 300A(1) are forcibly and mechanically coupled toeach other, thereby realizing the differential-lock state where thefirst and second driving wheels 50(1), 50(2) are forcibly driven at thesame speed.

Preferably, as illustrated in FIG. 6, the differential-lock connectingshaft 660 may be provided with a biasing member 680 for biasing at leastone of the first and second coupling-shaft-side couplings 670 to thecorresponding brake-shaft-side coupling 650.

With this structure, it is possible to enhance the efficiency of theoperation for switching between the differential state and thedifferential-lock state.

In the wheel motor device 300A(1) according to the present embodiment,there is only a single position at which the brake shaft 610 can beinstalled (see FIG. 5).

Namely, in the present embodiment, the brake shaft 610 can be supportedat a single position which is just opposite from the motor shaft 420with the rotational axis line of the first output member 350(1) as areference (namely, which is displaced by about 180 degree from the motorshaft 420 about the rotational axis line of the first output member350(1)). However, instead of this structure, the brake shaft 610 may besupported at plural positions about the rotational axis line of thefirst output member 350(1).

FIG. 7 illustrates an end view of a wheel motor device 300A′ accordingto a modified embodiment of the present embodiment, corresponding toFIG. 5.

As illustrated in FIG. 7, the wheel motor device 300A′ according to themodified embodiment includes a gear case 530′, instead of the gear case530.

The gear case 530′ has plural brake-shaft bearing portions 615 a, 615 bcapable of supporting the brake shaft 610 at plural positions about therotational axis line of the first output member 350(1) which ispositioned coaxially with the rotational axis line R of thecorresponding driving wheel.

The gear case 530′ is also configured so as to be capable of supportingthe mounting stay 632 and the fixed-side brake pad 635, at pluralpositions corresponding to the plural brake-shaft bearing portions 615a, 615 b.

Namely, as illustrated in FIG. 7, the gear case 530′ includes the pluralbrake-shaft bearing portions 615 a, 615 b positioned around therotational axis line of the first output member 350(1), and pluralmounting stay mounting portions 616 a, 616 b and plural fixed-sidebrake-pad mounting portions 617 a, 617 b corresponding to the pluralbrake-shaft bearing portions 615 a, 615 b.

By employing the configuration where the brake shaft 610 can beinstalled at the plural positions about the axis line of the firstoutput member 350(1) as described above, it is possible to enhance thedegree of freedom in designing the position at which the brake mechanism600 is installed.

Preferably, the plural brake-shaft bearing portions 615 a, 615 b capableof supporting the brake shaft 610 include first and second bearingportions 615 a, 615 b which are symmetrical to each other with animaginary vertical plane VP as a reference, which passes through therotation axis line of the first output member 350(1).

With this structure, in the case where the pair of wheel motor devices300A′ are employed as a first wheel motor device 300A′(1) for drivingthe first driving wheel 50(1) and a wheel motor device 300A′(2) fordriving the second driving wheel 50(2), it is possible to have the brakeshafts 610 in the first and second wheel motor devices 300A′(1),300A′(2) positioned coaxially to each other.

Namely, by arranging the brake shaft 610 in the first wheel motor device300A′(1) at one of the first and second bearing portions 615 a, 615 bwhile arranging the brake shaft 610 in the second wheel motor device300A′(2) at the other one of the first and second bearing portions 615a, 615 b, it is possible to have the brake shafts 610 in the first andsecond wheel motor devices 300A′(1), 300A′(2) positioned coaxially toeach other, while employing wheel motor devices with the same structureas the first and second wheel motor devices 300A′(1), 300A′(2).

Further, in the working vehicle 1A where the pair of rear wheels areformed to be the pair of driving wheels 50(1), 50(2) as in the presentembodiment, the brake shafts 610 preferably may be supported by bearingportions positioned in the front side of the vehicle than the rotationalaxis line of the corresponding driving wheels 50(1), 50(2), at a statewhere the wheel motor devices 300A′ are mounted in the working vehicle1A.

With this structure, it is possible to effectively prevent the brakeunit 630 from coming into contact with external obstructions during therearward movement of the vehicle.

Second Embodiment

Hereinafter, another embodiment of the wheel motor device according tothe present invention will be described, with reference to the attacheddrawings.

FIGS. 8 and 9 illustrate a schematic side view and a schematic rear viewof a working vehicle 1B to which the wheel motor device 300B accordingto the present embodiment is applied.

In the figures, the components same as those in the first embodiment aredesignated by the same reference characters and detailed descriptionthere of will not be repeated.

While the wheel motor device 300A according to the first embodiment isconfigured so as to output the driving power only to the correspondingone of the driving wheels (for example, the first driving wheel 50(1)),the wheel motor device 300B according to the present embodiment isconfigured so as to output the driving power to the corresponding one ofthe driving wheels (for example, the first driving wheel 50(1)) and alsooutput the driving power to the other driving wheel (for example, thesecond driving wheel 50(2).

FIGS. 10 and 11 illustrate a vertical cross-sectional view of the wheelmotor device 300B and an end view of the same taken along the line XI-XIin FIG. 10, respectively.

As illustrated in FIGS. 10 and 11, the wheel motor device 300B includesa speed-reduction gear unit 500B, instead of the speed-reduction gearunit 500 in the wheel motor devices 300A according to the firstembodiment, and also includes a second output member 350(2) foroutputting the rotational power to the other driving wheel (for example,the driving wheel 50(2)) on a side opposite from the corresponding onedriving wheel (for example, the driving wheel 50(1)) which is close tothe wheel motor device 300B.

Namely, the wheel motor device 300B includes the hydraulic motor unit400, the speed-reduction gear unit 500B, the first output member 350(1),the second output member 350(2) and the brake mechanism 600.

As illustrated in FIG. 10, the speed-reduction gear unit 500B includes agear case 530B for supporting the first and second output members350(1), 350(2) in a rotatable manner around their axis lines, and amechanical differential gear mechanism 70 accommodated within the gearcase 530B.

The gear case 530B is coupled to the motor case 430 in such a way as toform a casing of the wheel motor device 300B in cooperation with themotor case 430, similarly to the gear case 530 according to the firstembodiment.

The gear case 530B includes an inner-side case body 531B formedintegrally with the motor case 430, and the outer-side case body 532detachably coupled to the inner-side case body 531B.

In the present embodiment, as in the first embodiment, the extended wall431 c of the motor case main body 431 forms the inner-side case body531B. As a matter of cause, the inner-side case body 531B can be formedseparately from the motor case main body 431.

The gear case 530B supports the first and second output members 350(1),350(2) in such a manner that they are positioned coaxially to each otherand are rotatable around their axis lines independently to each other.

Specifically, the first output member 350(1) is supported by theouter-side case body 532 in a rotatable manner around the axis line soas to be positioned coaxially with the rotational axis line R of thecorresponding first driving wheel 50(1) in a state where its inner endis positioned within the gear case 530B and its outer end is extendedoutwards to be close to the first driving wheel 50(1).

Meanwhile, the second output member 350(2) is supported by theinner-side case body 531B in a rotatable manner around the axis line soas to be positioned coaxially with the rotational axis line of the firstoutput member 350(1) in a state where its inner end is positioned withinthe gear case 530B so as to face to the inner end of the first outputmember 350(1) and its outer end is extended outwards to be close to thesecond driving wheel 50(2).

As illustrated in FIG. 9, the second output member 350(2) is coupled toa wheel 55 of the second driving wheel 50(2) through a connecting shaft360 such that the second output member 350(2) rotate along with thewheel 55 around the axis line.

Further, the connecting shaft 360 can be either formed integrally withthe second output shaft 350(2) or formed separately therefrom, as amatter of cause.

In the present embodiment, as illustrated in FIG. 9, the connectingshaft 360 is coupled to a driving axle 56 of the wheel 55 of the seconddriving wheel 50(2) through a coupling member 365.

The driving axle 56 of the second driving wheel 50(2) is supported in arotatable manner about the axis line through a bearing bracket 365coupled to the mounting frames 15, as illustrated in FIG. 9.

The differential gear mechanism 70 includes a ring gear 710 placedcoaxially with the rotational axis line of the first and second outputmembers 350(1), 350(2), first and second side bevel gears 720(1), 720(2)respectively supported on the first and second output members 350(1),350(2) in a relatively non-rotatable manner, a pinion shaft 730 whichextends in the direction orthogonal to the rotational axis line of thefirst and second output members 350(1), 350(2) and which rotates aboutthe rotational axis line of the first and second output members 350(1),350(2) together with the ring gear 710, and a bevel pinion 740 supportedon the pinion shaft 730 in a relatively non-rotatable manner in a stateof being engaged with the first and second side bevel gears 720(1),720(2), as illustrated in FIG. 10.

As illustrated in FIG. 10, the ring gear 710 is engaged with both thedriving-side gear 511 provided on the motor shaft 420 and thedriven-side gear 621 provided on the brake shaft 610.

Namely, in the present embodiment, the driving-side gear 511 and thering gear 710 form the speed-reduction gear mechanism 510 and, also, thering gear 710 and the driven-side gear 621 form the speed-increasinggear mechanism 620.

In the present embodiment, it is possible to obtain an effect ofdifferentially driving the first and second driving wheels 50(1), 50(2)only by providing one wheel motor device 300B in a vicinity of one ofthe first and second driving wheels 50(1), 50(2), in addition tooffering the effects of the first embodiment.

Preferably, the differential gear mechanism 700 includes adifferential-lock mechanism 750.

In the present embodiment, as illustrated in FIG. 10 and FIG. 11, thedifferential-lock mechanism 750 includes a differential-lock slider 760which is rotatable about the rotational axis line of the first andsecond output members 350(1), 350(2) together with the ring gear 710 andwhich is movable in the direction of the rotational axis line, and adifferential-lock fork 770 which is supported by the casing in such away as to move the slider member 760 in the direction of the rotationalaxis line according to an operation from the outside.

As illustrated in FIG. 10, the differential-lock slider 760 is supportedby one (the second output member 350(2) in the illustrated embodiment)of the first and second output members 350(1), 350(2) on which one (thesecond side bevel gear 720(2) in the illustrated embodiment) of thefirst and second side bevel gears 750(1), 750(2) is supported, in such amanner that the slider 760 is relatively rotatable around and movablealong the axis line of the one output member.

More specifically, the differential-lock slider 760 has a supportedportion 761 supported by the corresponding output member, aradially-extended portion 762 extending outwards in the radial directionfrom the supported portion 761 so as to face to the one of the sidebevel gears, and an axially-extended portion 763 extending in thedirection of the rotational axis line from the radially-extended portion762 toward the ring gear 710.

The radially-extended portion 762 is selectively coupled to the one ofthe side bevel gears in such a manner that it is rotated together withthe one side bevel gear, according to the position of thedifferential-lock slider 760 with respect to the direction along therotational axis line.

More specifically, the radially-extended portion 762 has one of aconcave portion and a convex portion at the surface facing to the oneside bevel gear, and the one side bevel gear has the other one of theconcave portion and the convex portion at the surface facing to theradially-extended portion 762, so that the concave portion and theconvex portion are selectively engaged with each other or disengagedfrom each other according to the position of the differential-lockslider 760 with respect to the direction of the rotational axis line.

As illustrated in FIG. 10, the axially-extended portion 763 is engagedinto a slit 715 formed in the ring gear 710, so that thedifferential-lock slider 760 rotates together with the ring gear 710about the rotational axis line of the first and second output members350(1), 350(2).

The differential-lock fork 770 is configured so as to move thedifferential-lock slider 760 in the direction along the rotational axisline on the basis of an operation from the outside.

More specifically, the differential-lock fork 770 has rotational shaftportions 771 which are along the direction orthogonal to the rotationalaxis line and which are supported directly or indirectly by the casingin a rotatable manner around the axis line, and an engagement portion772 extending from the rotational shaft portions 771 such that its freeend portion engages with the differential-lock slider 760.

In the present embodiment, the differential-lock fork 770 has a pair ofrotational shaft portions 771 facing to each other across thedifferential-lock slider 760.

Further, a differential-lock arm 780 is coupled to one of the pair ofrotational shaft portions 771 in a relatively non-rotatable manner.

Namely, the differential-lock arm 780 has a supporting shaft portion 781supported by the casing in a rotatable manner around the axis line, andan arm portion 782 coupled to the supporting shaft portion 781 in such amanner it is positioned outside of the casing with being relativelynon-rotatable with respect to the supporting shaft portion 781.

With this structure, one of the pair of rotational shaft portions 771 iscoupled to the supporting shaft portion 781 in a relativelynon-rotatable manner about the axis line.

The arm portion 782 is operatively connected through a suitable linkmechanism (not illustrated) to a differential-lock operation member (notillustrated) capable of being manually operated which is positioned nearthe driver's seat 20.

The provision of the differential-lock mechanism 750 makes it possibleto easily switch between the differential state where the first andsecond driving wheels 50(1), 50(2) are differentially driven and adifferential-lock state where the first and second driving wheels 50(1),50(2) are forcibly driven at the same speed.

Further, while, in the present embodiment, the single wheel motor device300A is provided with the differential gear mechanism 700 so that therotational power from the motor shaft 420 is differentially transmittedto the first and second output members 350(1), 350(2), it is alsopossible to employ a side clutch or a side brake which is linked to asteering wheel, or a gear-less differential mechanism including twobidirectional clutches, instead of the differential gear mechanism 70.

While, in the first and second embodiments, the motor case 400 iscoupled to the mounting frames 15 at the side surface opposite from thecorresponding driving wheel for mounting the wheel motor device to thepair of main frames 11 as described above (see FIGS. 4, 10 and thelike), the present invention is not limited to the embodiments, as amatter of cause.

FIGS. 12 and 13, respectively, illustrate a vertical cross-sectionalview and an exploded perspective view of a wheel motor device 300Cmounted to the pair of main frames 11 through another mountingstructure, according to a modified embodiment of the present invention.

In FIG. 12 and FIG. 13, the components same as those of the first andsecond embodiments are designated by the same reference characters anddescription thereof will not be repeated.

As illustrated in FIGS. 12 and 13, in the wheel motor device 300C, themotor case main body 431 and the motor-side port block 432 have a firstand second frame mount bosses 430 a and 430 b, respectively, on theirupper surfaces. In the first and second frame mount bosses 430 a and 430b, plural first and second bolt holes 430 c and 430 d opened upwards arearranged in the lengthwise direction of the vehicle.

Meanwhile, a mounting stay 18 is coupled to an outer side surface of thecorresponding main frame 11.

The mounting stay 18 has a substantially T-shape in a cross-sectionincluding a vertical portion 18 a coupled to the outer side surface ofthe corresponding main frame 11 through fastening members such as boltsand a horizontal portion 18 b coupled to the lower end portion of thevertical portion 18 a. The horizontal portion 18 b has such a length inthe vehicle widthwise direction as to straddle both the bosses 430 a and430 b.

The horizontal portion 18 b is provided with first and second throughholes 19 a and 19 b corresponding to the first and second bolt holes 430c and 430 d, and the mounting stay 18 supports the motor case 430through plural bolts 19 c inserted through the first and second throughholes 19 a and 19 b and also threadedly inserted in the first and secondbolt holes 430 c and 430 d.

As described above, in the wheel motor device 300C, the first and secondbosses 430 a, 430 b are provided on the motor case main body 431 and themotor-side port block 432, which enables effectively accepting bendingstresses applied to the wheel motor device 300C.

Namely, both the first and second bosses 430 a and 430 b can be providedon the upper surface of the motor case main body 431, but this structurewill reduce the interval between the first and second bosses 430 a and430 b, thereby causing larger loads to be applied to the first andsecond bosses 430 a and 430 b.

On the contrary, the structure illustrated in FIG. 12 and FIG. 13 canincrease the interval between the first and second bosses 430 a and 430b, thereby enabling effectively accepting bending stresses applied tothe wheel motor device 300A.

Further, with the structure illustrated in FIG. 12 and FIG. 13, themounting stay 18 and the first and second bosses 430 a and 430 b havethe function of reinforcing the bonding between the motor case main body431 and the motor-side port block 432, thereby effectively preventingthe hydraulic fluid from being leaked through the bonding portionbetween the motor case main body 431 and the motor-side port block 432.

FIG. 14 illustrates a vertical cross-sectional view of a wheel motordevice 300D according to another modified embodiment of the presentinvention.

In FIG. 14, the components same as those in the above-explainedembodiments and modified embodiment are designated by the same referencecharacters and detailed description there of will not be repeated.

The wheel motor device 300D is mainly different from the wheel motordevice 300A according to the first embodiment in that the hydraulicmotor main body 410 is replaced with a hydraulic motor main body 410D ofa radial piston type and in that the speed-reduction gear mechanism 510is replaced with a speed-reduction gear mechanism 510D.

Specifically, the wheel motor device 300D includes a hydraulic motorunit 400D including the hydraulic motor main body 410D, aspeed-reduction gear unit 500D including the speed-reduction gearmechanism 510D, and the output member (the first output member 350(1) inthe illustrated embodiment) for outputting, to the corresponding drivingwheel (the first driving wheel 50(1) in the illustrated embodiment), therotational power whose speed has been reduced by the speed-reductiongear mechanism 510D.

The hydraulic motor unit 400D includes, as shown in FIG. 14, thehydraulic motor main body 410D of a radial piston type, the motor shaft420 supporting the hydraulic motor main body 410D in a relativelynon-rotatable manner, and a motor case 430D which supports the motorshaft 420 in a rotatable manner about the axis line and whichaccommodates the hydraulic motor main body 410D.

The hydraulic motor main body 410D includes a cylinder block 411Dconnected to the motor shaft 420 in a relatively non-rotatable manner.

The cylinder block 411D is supported in a rotatable manner around itsaxis line on a support shaft 470D, which is provided at the motor case430D so as to be positioned coaxially with the motor shaft 420.

The cylinder block 411D includes plural cylinder chambers 412 which aredisposed around the axis line and each of which extends in a radialdirection so as to have a first end opened to an inner circumferentialsurface of the cylinder block 411D that is in contact with the supportshaft 470D and a second end opened to an outer circumferential surfaceof the cylinder block 411D.

The hydraulic motor main body 410D further includes plural pistonmembers 413D respectively accommodated in the plural cylinder chambers412 in a reciprocating manner along a radial direction with the axisline as a reference.

In the present modified embodiment, the hydraulic motor main body 410Dfurther includes plural biasing members 414D that respectively press theplural piston members 413D radially outward.

The end on a radially outward side of the movable range of the pluralpiston members 413D is defined by a thrust ring 445D provided in themotor case 430D.

Specifically, the cylindrical thrust ring 445D is accommodated in themotor case 430D so as to surround the cylinder block 411D. That is, thecylinder block 411D is inserted into the thrust ring 445D in a state ofbeing supported by the support shaft 470D in a relatively rotatablemanner.

In the present modified embodiment, the thrust ring 445D has an innercircumferential surface having a substantially circular shape as viewedalong the axis line, and is fixed in an immovable manner in a state ofbeing eccentric with respect to the cylinder block 411D.

The wheel motor device 300D includes the hydraulic motor main body 410Dof a radial piston type as described above, thereby realizingminiaturization of the wheel motor device 300D in the vehicle-widthwisedirection, in comparison with the wheel motor device 300 including thehydraulic motor main body 410 of an axial piston type.

The motor case 430D is formed with the first motor-side hydraulic fluidchannel 215(1) which experiences a higher pressure at a time of theforward movement of the vehicle and the second motor-side hydraulicfluid channel 215(2) which experiences a higher pressure at a time ofthe rearward movement of the vehicle.

The wheel motor device 300D according to the present modified embodimentincludes the hydraulic motor main body 410D of a radial piston type, asdescribed above.

Therefore, the first motor-side hydraulic fluid channel 215(1) has afirst end opened to the outer surface of the motor case 430D to form thefirst motor-side hydraulic fluid port 216(1) and second ends branched soas to be fluidly connected to half of the plural cylinder chambers 412D.

Similarly, the second motor-side hydraulic fluid channel 215(2) has afirst end opened to the outer surface of the motor case 430D to form thesecond motor-side hydraulic fluid port 216(2) and second ends branchedso as to be fluidly connected to a remaining half of the plural cylinderchambers 412D.

The motor case 430D includes a motor case main body 431D that surroundthe hydraulic motor main body 410D and that forms an opening having asize that allows the hydraulic motor main body 410D to passtherethrough, the thrust ring 445D provided in the motor case main body431D through the opening, and a motor-side port block 432D detachablycoupled to the motor case main body 431D in such a way as to close theopening in a liquid-tight manner.

In the present modified embodiment, the support shaft 470D is integrallyformed with the motor-side port block 432D, and therefore, the first andsecond motor-side hydraulic fluid channels 215(1), 215(2) are formed inthe motor-side port block 432D.

The wheel motor device 300D is supported in a hanged manner by thecorresponding main frame 15 through the mounting stay 18, similarly tothe wheel motor device 300C.

In the wheel motor device 300D, the first and second bosses 430 a, 430 bare provided at an upper surface of the motor case main body 431D, asshown in FIG. 14.

The speed-reduction gear unit 500D includes the speed-reduction gearmechanism 510D, and the gear case 530 which accommodates thespeed-reduction gear mechanism 510D and which supports the first outputmember 350(1) in a rotatable manner around the axis line.

The speed-reduction gear mechanism 510D includes the driving-side gear511 with a small diameter, and an output gear 512D with a large diameterwhich is provided on the first output member 350(1) so as to be engagedwith the driving-side gear 511.

In the present modified embodiment, the output gear 512D is embodied byan internal gear.

The driven-side gear 621 provided at the brake shaft 610 is also engagedwith the output gear 512D in form of the internal gear.

In the present modified embodiment, the output gear 512D that is engagedwith the driving-side gear 511 to form the speed-reduction gearmechanism 510D and that is engaged with the driven-side gear 621 to formthe speed-increasing gear mechanism 620 is embodied by the internalgear, as described above.

The wheel motor device 300D with the configuration makes it possible tohave the positions of the axis lines of the motor shaft 420 and thebrake shaft 610 come close to the position of the axis line of theoutput member while sufficiently ensuring a speed reducing ratio of thespeed-reduction gear mechanism 510D and a speed increasing ratio of thespeed-increasing gear mechanism 620, thereby realizing miniaturizationof the wheel motor device 300D in a radial direction.

Finally, a wheel motor device 300 E will be described.

Although the wheel motor device 300E is inferior to the wheel motordevices according to the above explained embodiments and modifiedembodiments in terms of the degree of freedom in designing the brakemechanism 600, it could ensure the free space at the center in thevehicle widthwise direction as much as possible while realizingminiaturization of the brake mechanism 600 as much as possible.

FIG. 15 illustrates a vertical cross-sectional view of the wheel motordevice 300E.

In FIG. 15, the components same as those in the above-explainedembodiments and modified embodiment are designated by the same referencecharacters and detailed description there of will not be repeated.

The wheel motor device 300E is different from the wheel motor devicesaccording to the above-explained embodiments and modified embodiments inthat the brake mechanism 600 is configured so as to apply the brakingforce to the motor shaft 420.

Specifically, the wheel motor device 300E includes the hydraulic motorunit 400, a speed-reduction gear unit 500E including the speed-reductiongear mechanism 510, and the output member (the first output member350(1) in the illustrated embodiment) for outputting, to thecorresponding driving wheel (the first driving wheel 50(1) in theillustrated embodiment), the rotational power whose speed has beenreduced by the speed-reduction gear mechanism 510.

The speed-reduction gear unit 500E includes the speed-reduction gearmechanism 510, and a gear case 530E which accommodates thespeed-reduction gear mechanism 510 and which supports the first outputmember 350 (1) in a rotatable manner around the axis line.

The gear case 530E includes an inner-side case body 531E connected tothe motor case 430, and an outer-side case body 532E detachably coupledto the inner-side case body 531E so as to form the gear space 530S incooperation therewith.

As in the above-explained embodiments and modified embodiments of thepresent invention, the inner-side case body 531E is integrally formedwith the motor case 430.

The outer-side case body 532E is formed with a bearing hole 535Eallowing a first end 420 a of the motor shaft 420 on a side close to thecorresponding driving wheel to extend outward, as shown in FIG. 15.

Specifically, in the wheel motor device 300E, the motor shaft 420 hasthe first end 420 a on a side close to the corresponding driving wheelthat extends outward from the outer-side case body 532E. The brakemechanism 600 is provided at an outer surface of the outer-side casebody 552 e on a side close to the corresponding driving wheel so as toapply the braking force to the first end 420 a of the motor shaft 420.

The thus configured wheel motor device 300E makes it possible to ensurethe free space between the pair of wheel motor devices 300E larger thana wheel motor device 300F (see FIG. 16) in which the brake mechanism 300is positioned between the hydraulic motor unit 400 and thespeed-reduction gear unit 500 in the vehicle widthwise direction.

In the wheel motor device 300E, the brake mechanism 600 is preferablydisposed within the wheel 55, as shown in FIG. 15.

According to the preferable arrangement, it is possible to have thewheel motor device 300E come close to the corresponding driving wheel inthe vehicle widthwise direction as much as possible, thereby wideningthe free space as much as possible.

1. A wheel motor device applied in a working vehicle including a drivingpower source, a hydraulic pump main body operatively driven by thedriving source and a pair of first and second driving wheels facing toeach other along a widthwise direction of the vehicle, the wheel motordevice comprising a hydraulic motor main body forming an HST incooperation with the hydraulic pump main body, a motor shaft supportingthe hydraulic motor main body in a relatively non-rotatable manner, aspeed-reduction gear mechanism for reducing the speed of the rotationalpower output from the motor shaft, a first output member for outputtingthe rotational power whose speed has been reduced by the speed-reductiongear mechanism toward the corresponding first driving wheel, a casingaccommodating the hydraulic motor main body and the speed-reduction gearmechanism, and a brake mechanism selectively and operatively applying abrake force to the first output member, the wheel motor device beingcharacterized in that, the brake mechanism includes a brake shaftsupported by the casing, a speed-increasing gear mechanism forincreasing the speed of the rotational power output from the motor shaftand operatively transmitting the same to the brake shaft, and a brakeunit for selectively and operatively applying the brake force to thebrake shaft.
 2. A wheel motor device according to claim 1, wherein thecasing includes a motor case which supports the motor shaft at aposition displaced from a rotational axis line of the first drivingwheel in such a manner that the motor shaft is substantially parallel tothe rotational axis line of the first driving wheel and is rotatablearound its axis line and which accommodates the hydraulic motor mainbody supported by the motor shaft, and a gear case connected to a sideof the motor case which is close to the first driving wheel, the gearcase supporting the first output shaft so as to be positioned coaxiallywith the rotational axis line of the first driving wheel in a state ofbeing rotatable manner around its axis line and accommodating thespeed-reduction gear mechanism, the brake shaft is supported in arotatable manner around its axis line by the gear case at a positiondisplaced from the first driving wheel around the rotational axis lineof the first driving wheel, in such a manner that the brake shaft issubstantially parallel to the rotational axis line of the first drivingwheel and an end portion of the brake shaft on a side away from thefirst driving wheel is extended outward from the gear case, and thebrake unit includes a brake disk supported by the outwardly-extendingend portion of the brake shaft in a relatively non-rotatable manner, andis configured so as to selectively apply the brake force to the brakedisk on the basis of an operation from the outside.
 3. A wheel motordevice according to claim 2, wherein the gear case is capable ofsupporting the brake shaft at plural positions around the rotationalaxis line of the first output member.
 4. A wheel motor device accordingto claim 3, wherein the plural positions include first and secondportions which are symmetrical to each other with an imaginary verticalplane as a reference, the imaginary vertical plane passing through therotation axis line of the first output member.
 5. A wheel motor deviceaccording to claim 2, wherein the brake unit includes a mounting staydetachably connected to the gear case, a brake operation shaft supportedin a rotatable manner around its axis line by the mounting stay in astate that its axis line extends substantially parallel to a disksurface of the brake disk and its first end portion having anon-circular cross-sectional shape overlaps with the brake disk asviewed along the rotational axis line of the brake disk, and a push-sidebrake pad supported by the first end portion in such a manner as to comeclose to or separate from the brake disk in accordance with the rotationof the brake operation shaft about the axis line.
 6. A wheel motordevice according to claim 5, wherein the brake unit further includes afixed-side brake pad detachably supported by the gear case in such amanner as to face to the push-side brake pad across the brake disk.
 7. Awheel motor device according to of claim 2, further comprising abrake-shaft-side coupling supported in a relatively non-rotatable mannerby a portion of the brake shaft which is away from the first drivingwheel than the brake disk, wherein the brake-shaft-side coupling has aconcave/convex engagement portion at an end surface on a side oppositefrom the corresponding first driving wheel, the concave/convexengagement portion being opened toward the other second driving wheel.8. A wheel motor device according to claim 1, further comprising asecond output member which is operatively connected trough thespeed-reduction gear mechanism to the motor shaft and which outputs adriving force toward the second driving wheel.
 9. A wheel motor deviceaccording to claim 8, wherein, the first and second output members arepositioned coaxially with each other, the wheel motor device furthercomprises a differential gear mechanism including a ring gearoperatively connected to the motor shaft, first and second side bevelgears respectively supported on the first and second output members in arelatively non-rotatable manner, a pinion shaft rotating along with thering gear, and a bevel pinion supported on the pinion shaft in arelatively rotatable manner in a state of being engaged with the firstand second side bevel gears, a driving-side gear with a small diameterprovided on the motor shaft so as to engage with the ring gear forms thespeed-reduction gear mechanism in cooperation with the ring gear, and adriven-side gear with a small diameter provided on the brake shaft so asto engage with the ring gear forms the speed-increasing gear mechanismin cooperation with the ring gear.
 10. A wheel motor device according toclaim 1, wherein, the motor shaft is displaced from the rotational axisline in a state of being substantially parallel to the rotational axisline, the first output member is disposed coaxially with the rotationalaxis line of the first driving wheel, the speed-reduction gear mechanismincludes a driving-side gear with a small diameter which is provided onthe motor shaft in a relatively non-rotatable manner, and an output gearwith a large diameter which is provided on the first output member in arelatively non-rotatable manner and which is engaged with thedriving-side gear, the output gear being embodied by an internal gear,the brake shaft is provided with a driven-side gear with a smalldiameter which is engaged with the output gear, and the output gear andthe driven-side gear form the speed-increasing gear mechanism.